Kristen Stewart refused to celebrate her 21st birthday on the set of the last Twilight movie, because she didn't want her milestone to overshadow the wrap party for the final film.

The actress turned 21 in April (11) and her big day coincided with a bash to mark the end of The Twilight Saga: Breaking Dawn Part 2 shoot.

However, rather than revel in the attention, Stewart attempted to downplay her birthday - but her co-stars had a surprise ready for her.

Actress Julia Jones tells E! Online, "There was a huge cake for her, but she didn't want it to be about her birthday; she wanted it to be about the wrap party. So they didn't bring it out.

"At a certain point, myself and a few other people were like, 'Wait a minute. Where is Kristen's cake?' We went back into the kitchen and demanded they bring the cake out. It was quite a scene.

"She was totally fine (about the celebration) but I understand, because the wrap party was a big deal. I'm very shy about my birthday also. You don't want any more attention."